Supported catalysts used in Fischer-Tropsch reactors, including for example, slurry bubble column reactors and continuously stirred tank reactors (“CSTR”), are subjected to agitation causing significant collisions and frictional forces. Such collisions and forces can result in damage mechanisms which, over time, may cause attrition of the catalyst and/or catalyst support. Attrition of catalyst and/or catalyst support raises operating costs due to increased catalyst requirements. Moreover, attrition results in the production of fines which must be removed by filtration. The filtration process may cause loss of active catalyst in addition to removal of the fines, thereby further raising operating costs.
Catalyst supports used in fixed bed reactors may also be subjected to movement and collisions during batch or continuous regeneration processes. Consequently, some attrition may occur with fixed bed reactors. Moreover, catalyst supports, such as shaped extrudates, frequently show appreciable attrition during catalyst production, e.g., cobalt deposition onto the support. In such instances, the attrited fines must be removed from the catalyst product prior to use to prevent reactor plugging.
Attempts to reduce catalyst attrition include non-aqueous processes. Such processes require use of a non-aqueous solvent because the silicating agent used reacts rapidly with water which would displace the desired reaction of the silicate, with the hydroxyl or oxide groups on or near the surface of the catalyst support.
Yet another known process uses ethanol, i.e. non-aqueous, solutions of tetraethoxysilicate to deposit silicon onto catalyst supports for the purpose of suppressing the solubility of the support in aqueous acidic solutions which are typically encountered during preparation of the supported catalyst.
However, the use of non-aqueous solvents raises costs due to the cost of the solvents themselves as well as the cost of specialized equipment.